When genetics meets epigenetics: deciphering the mechanisms controlling IFNg expression and tuberculosis susceptibility.

ALVAREZ GUADALUPE INES; HERNANDEZ DEL PINO RODRIGO EMANUEL; BARBERO ANGELA MARIA; PAMERO DOMINGO; GARCIA VERONICA; PASQUINELLI VIRGINIA

Buenos Aires

Congreso; IV Congreso de la Sociedad Latinoamericana de Inmunodeficiencias (LASID), LXIII Reunión de la Sociedad Argentina de Inmunología (SAI) y II Reunión FAIC (French-Argentinean Immunology Congress).; 2015

Millions of new tuberculosis (TB) cases are reported annually. Human genetic identification iscrucial for understanding TB pathogenesis. IFNgis key in the protective immunity against M.tuberculosis (Mtb). We studied 7 Single Nucleotide Polymorphism (SNPs) on IFNgrelated genes,to find new genetic markers of TB susceptibility.DNA was obtained from whole blood of patients with TB (PTB), Healthy Donors (HD), and LatentTB Individuals (LTBI). IFNg+874 A/T SNP was studied by ARMSPCRand we found the highestfrequency of AA genotype in PTB vs HD and LTBI. Moreover, PTB with AA genotype had thelowest IFNglevels in supernatants of MtbstimulatedPBMC.We also studied 262A/T, 188A/G (PCRRFLP)and +1343 G/T (sequencing) SNPs at thesignaling lymphocytic activation molecule (SLAM, an inducer of IFNgagainst Mtb). But they werenot suitable as genetic markers of TB susceptibility, as the most frequent genotype for each SNPwere overrepresented in all groups.3 SNPs at the SLAM associated protein (SAP, 631A/G, 494A/G and 346C/T), an IFNginhibitor were studied. We found an AA/GG/TT haplotype that was more frequent in PTB and LTBI,showing the lowest frequency in HD. IFNgwas significantly lower for the AA/GG/TT haplotype vsGG/AA/CC, while the opposite results were observed for SAP expression. Finally, we found anIFNg/SAP haplotype AA/AA/GG/TT that could be a strong marker of TB susceptibility inArgentina.We found, higher percentages of DNA methylation at the IFNg53CpG site in PTB compared withLTBI, showing epigenetic regulation. We also studied two gene repressors, Blimp1 and TLE4,which recruit to chromatin DNA Histone deacetylases (HDACs). After Mtb stimulation Blimp1 andTLE4 shown an expression pattern opposite to that observed for IFNg.Moreover treatment with aHDAC inhibitor significantly increased IFNgin Mtbstimulatedcells, suggesting that Blimp1/TLE4could be involved in the epigenetic control of IFNgduring Mtb infection.